Multi-layer lubrication utilizing encapsulating coating



United States Patent 3,269,943 MULTl-LAYER LUBRICATIUN UTILIZING ENCAPSULATENG COATING David E. Armstrong, Doylestown, and Gerald P. Roeser,

Lahaska, Pa, assignors to Horace T. Potts, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Original application June 12, 1961, Ser.

No. 116,527, now Patent No. 3,191,286, dated June 29, 1965. Divided and this application June 17, 1965, Ser.

5 Claims. (Cl. 252-12) This application is a division of our copending application, Serial No. 116,527, filed June 12, 1961, now US. Patent 3,191,286.

This invention relates to a novel lubricating composition used for metal which is to be subjected to forming operations. A removable, substantially non-destructible solid synthetic plastic film-hereinafter known as the encapsulating filmis applied to said metal and a novel lubricant coating is applied to said resin film to facilitate forming the encapsulated metal against a hard metal die.

Conventional liquid lubricants of the mineral oil type, known synthetic lubricants, such as the stable non-volatile esters of organic and inorganic acids, the metal soaps and the silicone oils, the fluorocarbons, and the naturally occurring fats, oil, waxes and rosin oils, have each been found to be unsatisfactory for deforming of metal against metal in the cold, by reason of metal scoring and seizing.

Solid film lubricants such as graphite, copper phthalocyanine, molybdenum disulfide, alkaline earth oxides and other polyvalent metal sulfides, and certain polymers, such as trifluorethylene polymers and tetrafluorethylene polymers have also been proposed for lubrication of metal-tometal parts under extreme pressure conditions, but have also been found to be unsatisfactory for deforming of metal.

Although the lubricating system of the present invention has some superficial similarity to the solid film lubricants which are well-known in the art, there are essential differences in the specific materials which are used underlying the novelty of the present compositons.

The new concept of the present invention and its inherent simplicity are better understood by comparing the encapsulating principle of the present invention with conventional (unmodified) solid film lubricants. The invention employs as a critical feature thereof the new principle of reduced coefficeint of friction between metal-to-metal through interposition of a physically permanent plastic barrier between one metal surface being deformed and the other metal surface of the die or forming structure. The coeficient of friction is no longer that of lubricant between metal and contacting metal. Instead, it is the coefficient of friction between the plastic capsule about the metal workpiece and the metal of the die. This coefiicient of friction is not the inherent value of the plastic material of the capsule since it is necessary, in accordance with the invention, to reduce the coefficient of friction between the plastic capsule and metal of the die to a value which permits the plastic material to remain dimensionally intact yet allows the underlying metal of the workpiece to flow under tensile forces which may be in excess of 100,000 pounds per square inch.

In accordance with the invention, a unique surface treatment of the encapsulating film is effected by treatment with a lubricating surface modifier (hereinafter called the modifier) having a melting point in the range of 37110 C. and a lubricating action between the capsule and a steel die whereby an extremely low coefficient of friction is achieved. This permits successful use of the lubrication of the invention at room temperature for cold-forming of metals.

The lubricating modifier is characterized chemically by its low coeflicient of friction against plastic and metal, by its high degree of aflinity for the base plastic material of the capsule due to the presence of highly polar nitrogen or oxygen atoms or both types of atoms in the molecule of the modifier and is characterized physically by its uniquely narrow melting range lying between 37 C. and 110 C.

Examples of chemical species of modifier bearing polar nitrogen atoms and groups include fatty amines and nitriles substituted with long hydrocarbon radicals of melting point lying between 37 C. and 110 C., e.g., stearyl nitrile, nonadecylic nitrile, arachidyl nitrile and chlorinated and fluorinated derivatives of these nitriles within this melting range, distearyl amine, arachidylamine and chlorinated and fluorinated derivatives of these.

Examples of modifiers having melting point of 37 C.- 110 C. including both the polar oxygen and nitrogen group are the fatty amides and quaternary compounds substituted with fatty acid esters and preferably of polyamines and polyhydroxyamines. In the first category of fatty amide there may be used oleamide, ethylene stearamide, mixtures of oleamide and stearamide, hydroxy stearamide, mixtures of hydroxystearamide and stearamide. These fatty amides may be mixed with fatty amines, for example, mixtures of stearamide with oleylamine (primary amine) in proportions as will give a melt ing point above 37 C.

In the second category of quaternary ammonium compounds there may be used such compounds as fatty acid esters or wax esters of ethylene di-amine shown in US. Patent No. 2,695,243 or of N,N,N',N-tetrakishydroxyethyl ethylenediarnine as are shown in U.S. Patents Nos. 2,878,144 and 2,878,273.

The materials selected from these patents are those having a melting point above 37 C. and less than 110 C. Indeed, at a melting point of less than C. these ma terials appear to operate more effectively.

Thus, in general, it is seen that fatty nitrogen compounds, amides, amines, amine salts, nitriles and quaternary compounds in the melting point of 37/ll0 C. are generally operative as the lubricating modifier.

The modifier is preferably a low melting amide of oleic acid, a low melting polyglycol, a low melting, self-emulsifying wax such as myristyl myristate, or a low melting, low molecular weight linear polymer of ethylene or propylene, or equivalent low melting, low molecular weight copolymer of ethylene and propylene. These materials are applied either as a solution or dispersion in a volatile medium, such as water, or an organic solvent, or as a hot melt.

As a result of this treatment, the surface of the solid encapsulating film is physically altered to exhibit a kinetic coefficient of friction against a polished steel-forming a surface of about 0.01-0.02 and a static coefficient of friction of substantially the same order.

The lubricated surface stratum which is achieved by this treatment to impart high lubricity and a coefficient of friction lying between 0.01 and 0.02 is extremely thin and surprisingly may or may not be a continuous coating. It has been discovered that the low melting lubricant, be it the low melting amide, or the low molecular weight polyglycol, or the low molecular weight ethylene polymer, when applied from dispersions form islands or particles, but that under cold-forming pressure or at slightly elevated temperature, e.g., up to about 100 C., either melts or softens to a very thin lubricating layer at the interface between the film encapsulated workpiece and the die. Of course, these lubricants deposit continuous films when applied molten and said continuous films behave like the discontinuous films described above.

With the uniquely suitable lubricant components of the present invention, there is found to exist a limited compatibility between the lubricating coating and the hard non-destructible underlying encapsulating resinous base so that the lubricant stays on top of the film base. It has been discovered by trial and error that there must be no substantial penetration or softening of the plastic film by solvent carriers for the surface modifying agent, or by the agent itself, since this would weaken the encapsulating film to permit tearing which would lead to scoring, then to metal-to-metal seizing and galling during coldforming.

It has been discovered that the encapsulating resin film must be substantially incompressible. Also a minimum adhesion shear strength of the solid lubricant-carrying film is needed to prevent separation from the underlying metal material which is thus protected during cold-forming. A high value of modulus of elasticity is a desirable characteristic of the resin.

The minimum value of adhesion strength of the encapsulating film to the base metal under cold-forming forces is at least 2 kilograms per square millimeter, or at least 600 pounds per square inch. Incompressibility, adhesion, hardness and toughness in the film provide a non-destructible capsule which is uniquely suited for cold-forming of metals under forces beyond the tensile limit of the strongest metals. The tensile strength of the tough encapsulating film material must be a minimum of 3000 pounds per square inch, preferably about 4500 pounds per square inch in order to maintain the integrity of the plastic capsule under metal flow conditions. The elasticity of the encapsualting film as measured by percent elongation must be at least 3 percent to prevent rupture during the forming operation.

Also, the encapsulating film must have a hardness value of at least Brinell in order to provide a substantially non-destructible film for carrying the surface lubricant having a low coefficient of friction against the metal die in order to prevent rub-off during the forming operation or wearing metal parts.

Chlorinated rubber is preferred as the encapsulating film material which is to be subjected to surface modification for providing a low coefficient of friction against metal.

The encapsulating film thickness is readily controlled between /2 to 3 mils in thickness. In the case of chlorinated rubber, this encapsulating film has a tensile strength of about 2500-5000 p.s.i., a modulus of elasticity of about 140,000 pounds, and elongation of up to about 4%.

Other hard, strong, and metal-tenacious resins may also be used, such as certain vinyl polymers, e.g., a copolymer of 87%95% vinyl chloride, 12%l3% vinyl acetate, and from 0.52.5% of an unsaturated carboxylic acid such as acrylic acid or maleic acid and a copolymer of 65-85% vinyl chloride and -15 of vinylidene chloride.

Other operable film materials include polymethyl methacrylate, polyethyl methacrylate and their coploymers; polyvinyl acetals including formals, acetals, and butyrals;

bisphenol epoxides of the high molecular weight type, like Epon 1009; cellulose acetobutyrate; vinyl chloride-vinyl acetate copolymer, like VYI-IH or Geon 428; chlorinated polyethylene or polypropylene.

To this fixed capsule film which is unsatisfactory per se as a lubricant there is applied a special coating, preferably a separate formed surface of lubricating material which is capable of movement on the encapsulation film.

As a result, the film is converted to a capsule-bearing lubricant surface by the specific means taught by the invention to achieve a much lower coefficient of friction of plastic film against metal, e.g., steel, iron, copper, titanium, zirconium etc., than could be achieved by any known lubricant per se, liquid or solid, directly interposed between the two metal surfaces and being under the conditions of metal flow.

It is an advantage of the invention that the lubricant solid encapsulating film and surface lubricant thereon are readily dissolved in common solvents either for coating purposes or for removal purposes at room temperature. Such common organic solvents may be used as chlorinated hydrocarbon solvents, solvent naphtha, amyl acetate, ethyl acetate, ethylene glycol monomethyl ether, aromatic hydrocarbon solvents, mixtures of aromatic and high boiling aliphatic hydrocarbon solvents, and ketones such as acetone, methyl ethyl ketone, amyl ketone, etc.

It is a further advantage of the invention that the formation of the solid polymer encapsulating film and surface lubricant onto the base surface does not need elevated temperatures to create adhesion thereto. Excellent adhesion is obtained by coating the base polymer from a solution or a water dispersion and by air drying at room temperatures.

In summary, the physical characteristics of the encapsulating film which have been discovered to be necessary in accordance with the invention are: (1) good hardness, (2) high tensile strength, (3) high film integrity (resistance to shear and creep), (4) good flexibility, and (5) resistance to thinning by compression.

Such polymers as polystyrene are wholly unsuitable by reason of excessive brittleness and low impact resistance. These cause the encapsulating film to fracture under load. Polyvinyl acetate and high butyrate-containing cellulose acetobutyrate encapsulating films are unsuitable because of excessive elongation and excessive cold flow.

Alcohol soluble nylon which is much more elastic than either of the suitable vinyl chloride-vinylidene chloride encapsulating polymers or suitable vinyl chloride carboxylic acid copolymer or the preferred chlorinated rubber polymer of the invention is also unsuitable because of excessive elongation. The nylon base material has a high elongation and undergoes excessive cold flow. The high tensile strength of the nylon base polymer, about 4000- 7000 p.s.i., and its excellent adhesion to metal do not compensate for its excessive elongation.

In a preferred embodiment of the invention using a hard chlorinated rubber (specific gravity 1.501.65 and containing about 67% chlorine) as the encapsulating material, excellent adhesion is achieved to an underlying cleaned body of stainless steel. The Brinell hardness value of the chlorinated rubber capsule is about 25-30. This hardness is not altered by modification with the preferred surface coating of oleamide under the application of metal flow cold-forming forces.

There is observed no change in the film dimensions. Neither film continuity nor thickness are altered under a cold-forming pressure of 100,000 p.s.i. or higher in the case where oleic acid amide is applied as a top coating over chlorinated rubber or as a modifier in a stratified coating admixed with chlorinated rubber.

Initially the surface coating of oleic acid amide is present at room temperature as a non-tacky discontinuous thin coating which is dry to the touch and which can be scraped off readily. However, the effective surface hardness is that of the main body of the film. Furthermore, when all the particles and islands are smoothed out during the cold-forming operation, the lubricant coating remains on top of the encapsulating resin base as a hard film, much harder than Teflon for example.

The chlorinated rubber encapsulating body may be first applied as a base film to the metal part and the oleic acid amide thereafter applied as a top coating or the chlorinated rubber and the oleic acid amide may be mixed in the original coating solvent for encapsulation and lubrication by a single application. By adjusting the solids concentration and controlling the solvent selection, a stratification of oleic acid amide over the encapsulating base resin is achieved, and the lubricant amide component effectively stratifies on the surface of the encapsulating film due to its difference in density and limited compatibility in the presence of organic solvent.

To illustrate stratifying mixtures there are prepared solvent solutions of chlorinated rubber and oleic acid amide in proportions by weight of 50/50, 33/66 and l0/90 at solids in xylol. This solution deposited by brushing as a continuous film 23 mils thick on a degreased stainless steel tubular blank and after air drying results in stratification with the amide separating as blotches and particles on the surface. The highly-adherent, hard, tough chlorinated rubber base stratum is oriented as a continuous solid encapsulating film about and at the metal interface. The soft oleic acid amide surface modifier stratum after thorough drying in sufficiently thin layer separates as a discontinuous dry surface in the form of islands or particles. Thorough drying is necessary to prevent failure of the encapsulating film. Stratification occurs best at the proportions of 33/66 to 10/90.

The use of an organic solvent for depositing the lubricant coating on the solid encapsulating film base is not necessary and indeed, is not preferred in practice. It is preferred that there be used an aqueous volatile vehicle which does not soften the resin capsule. An oleamide emulsion works better than a solvent solution.

A low molecular weight polymer in the form of an aqueous emulsion of linear polyethylene, molecular weight 400-5000 and melting point about 90l05 C. also works well. This latter emulsion or an aqueous solution of waxy polyethylene glycol or copolymer, molecular weight of MOO-20,000 can be used or can be blended with an organic solvent solution of chlorinated rubber or vinyl polymer as specified hereinabove to form an oil-in-Water emulsion by conventional emulsifying and mixing practice (preferably using a colloid mill). These aqueous emulsions can dry to stratified condition in the same manner as the organic solvent solutions.

The type of chlorinated rubber which is preferably ernployed in the examples below to produce the substantially non-destructible solid encapsulating film of the invention is of medium to high molecular weight at a chlorine content of about 67% as evidenced by good solu bility in aromatic hydrocarbons such as benzene, toluene or xylene (up to about 40%) total solids by weight of hydrocarbon solvent and of medium to low viscosity in said hydrocarbon solution. Satisfactory encapsulating films have been produced as shown in Example 1 with chlorinated rubber having a specific viscosity value of 0.70 measured in dimethyl formamide solvent, 1 gram of chlorinated rubber per deciliter of dimethyl formarnide solvent. The viscosity and molecular weight are such as pointed out above as will deposit a film up to about 3 mils in thickness by dip coating at solids, in xylol solvent onto clean steel. The so-deposited encapsulating film is non-inflammable, stable to ultraviolet light, extremely impermeable to water and highly resistant to attack by alkali or acid.

If the encapsulating film is plasticized with primary chemical plasticizers such as tricresyl phosphate or dibutyl phthalate or with such secondary plasticizers as lard oil, linseed oil, tung oil, etc. it is unsatisfactory because of softness and tends to tear away from the underlying metal causing seizing and galling.

If the molecular weight of the preferred chlorinated rubber encapsulating resin is too low, e.g., substantially less than specific viscosity value of 0.50 measured in a dimethyl formamide, then the encapsulating film tends to flake off from the metal base and reproducible lubrication during metal forming without destruction of the capsule is not obtained.

If the specific viscosity is too high, e.g., above 0.85, the solutions become excessively viscous to make it difficult to brush, spray, dip or cast the coating from organic solvent solution such as xylol.

This difiiculty is not encountered when chlorinated rubber encapsulating film is applied out of an aqueous dispersion (oilin-Water type). The advantage of slightly higher encapsulating film thickness is desirable for some applications, improving rather than lessening lubricating efficiency with the special lubricant materials of the invention applied ot the film capsule.

Obviously, the metal workpiece is carefully cleaned and dried before encapsulating. Where rough metal surfaces are encountered it may be desirable to use heavier encapsulating film thicknesses, e.g., in excess of 3 to 4 mils in order to provide a smooth and level outer encapsulating film surface. In any event, the thicknes of the encapsulating film is always sufficient to obliterate surface imperfections or roughness in the underlying metal.

The solvent for the encapsulating resin should be completely volatile on standing at room temperature to facilitate air drying. If high boiling oily solvent residues remain after air drying, these soften the capsule and prevent attachment of the film to the base for cold-forming the encapsulated metal in a die.

The capsule for the metal workpiece when formed of vinyl chloride-vinyl acetate-carboxylic acid copolymer has the obvious advantage over chlorinated rubber in being capable of being adapted to be thermoset under the action of heat and thereby converted from a softer, fusible and solvent-soluble condition to a harder, infusible and solvent-resistant condition.

Carbamide res-ins and phenolic resin which are heat convertible and compatible with vinyl chloride resins of the VMCH type and of the VAGH type may be mixed with said vinyl resin, for example, m'elami-ne-formalde hyde resin, urea-formaldehyde resin and phenol-formaldehyde resins in the amounts recommended and known for addition to these tripolymer resins available commercially under these trade names VAGH and VMCH from Union Carbide Company. When these heat-setting resins are added, the encapsulting films become thermoset by baking at elevated temperatures of 300-450 F. for 10- 30 minutes Without any substantial alteration of the necessary hardness, adhesion, elongation and tensile strength characteristics.

In similar manner these same additions of carbamide or phenolic resin may be employed to render thermoset the other encapsulting resins described previously.

Obviously these thermoset encapsulating films may in accordance with the invention be employed as permanent decorative coatings simultaneously with achieving the lubricant function by modifying with oleamide rather than as temporary removable lubricant coatings. Suitably pigmented, these thermoset encapsulating films after surface modifications by the amide, glycol or olefin polymer can serve for both solid encapsulating film and lubricant film and a decorative function for long lasting coating.

Thus the requirement in accordance with the invention for easy solubility in an organic solvent holds for the case where clean bare formed metal is to be produced but when insoluble thermosetting polymer is used the finish can be left on the formed form,

Thus, it will be appreciated that the lubricant encapsulating films of these vinyl polymer types are also useful where decorative protective finishes are desired. When the metal stock is designed to be finished, this may be done in accordance with the invention prior to fabricating, the thermoset coating fulfilling both protective and lubricating functions. As an example, lacquer-coated corrugated iron or aluminum sheet, metal siding for the home, decorative paneling, cans, pails and enclosures may be first coated and then formed by cold-forming standard methods to provide a finished coated product.

Also ducting for air conditioning and heating, metal hardware, metal wheels for automotive or farm equipment cold-stamped or cold-formed may be provided with the thermoset coating. Obviously, any of these articles which are to be put in final form of bare shiny metal are used with the thermoplastic encapsulating film and the encapsulating film is removed. Either of these varieties, thermoplastic or thermoset, may be used for lubricating and/ or finishing window framing of aluminum, magnesium or steel, for wire drawing and for temporary or permanent protection of die surfaces. The lubricant encapsulating film is particularly adapted for coating air cylinders in recoil mechanisms and shock absorbers, for protecting gear trains and for hoists. Lubrication may be beneficially applied to rollers and/ or sprockets coming into contact with hard metal in conveyer mechanisms. Valves and cam mechanisms may be lubricated. Bearing surfaces, whether straight journal, roller or taper type in use as wet or as dry bearings, may also be lubricated to good advantage. Leaf springs as are used in trucks and automobiles may be given a substantially indestructible solid encapsulating film lubricant coating to improve their performance. Similarly, rotating seals, stufiing boxes and packing glands for moving machine parts can be uniquely coated with a non-destructible coating and operate in a fashion as can entirely eliminate oil seals. By employing a fluid bed for the coated member of powdered amide oil is entirely eliminated, dirt and foreign matter which ordinarily are entrapped in liquid oil type lubricants can be completely excluded and an essentially dry lubrication system is achieved.

The following are detailed working examples illustrating the application of the solid lubricant encapsulating film of the invention and the uses which are made for cold-forming of metals.

EXAMPLE I To illustrate the extreme force conditions which the embodiment of organic solvent-soluble thermoplastic encapsulating film and lubricant modifier in accordance with the invention must withstand, this example describes the simultaneous cold-forming and cold-sizing of a 90 L of stainless steel, carried out by the method and the apparatus of copending application, Serial No. 286,880, filed May 28, 1963. This cold-forming operation is selected as a typical example of the application of the multi-layer lubrication of the present invention. Another method and apparatus which demonstrates the utility of the present invention is that disclosed and claimed in US. Patent No. 2,971,556, granted February 14, 1961, to Armstrong et al.

A beveled tubular blank of circular cross section of stainless steel 6% inches long length, 6% inches short length, .109 inch wall thickness and 2.375 inches outer diameter, is coated with an organic solvent-soluble thermoplastic encapsulating film by brushing onto the chemically cleaned metal base. The encapsulating film is applied as a lacquer consisting of a xylol solution of chlorinated rubber (25% solids in solvent) in a single coat and a top coating of oleic acid amide solids) in 1,1,1- trichloroethane is applied thereto. The first coat is completely dry before the second coat of lubricant is applied. The base encapsulating coat is about 1 to 2 mils in thickness and the top lubricant coating, is about 1 mil thickness. The total encapsulating plastic film and lubricant thickness is about 2 to 3 mils. The upper stratum of high lubricity is formed in the top coating step as a dis- 2% continuous surface layer consisting of particles of oleic acid amide which, under high compressive forces at room temperature, becomes continuous.

The blank is then subjected to forming forces of 1,100 pounds and counterthrust forces of about 500-600 pounds in the apparatus of copending application Serial No. 286,880 and with a clearance of about 0.007-0.0l2 inch in the die.

Under the cold-forming forces the shorter length of 6% inches in the stainless steel is uniformly thickened by controlled metal flow up to an increase in thickness of about 30% in the 510 of are at the maximum bend and then is decreased uniformly in thickness to the original thickness value in the following 510 of are at the maximum bend. The longer length is thinned by controlled metal flow to a value of about 5% less than original thickness at the maximum radius of bend, this slight thinning being gradual and continuous along the larger peripheral arc to merge into the unchanged area of stock having the original thickness. There is no measurable thinning of the composite solid film lubricant.

A second L was made in the same apparatus and using the identical encapsulating film of chlorinated rubber as in the first part of this example, but using conventional commercial, water-emulsified lard oil lubricant which is the recommended lubricant for tin shop cutting, punching and forming. The commercial lard oil lubricant is identified as lube A and the forming of the L is described in detail below in comparison to the forming of the 90 L using oleamide lubricant coating, lube B, identified hereinafter.

From the foregoing example it will be seen that the adhesion, hardness, toughness, incompressibility and low elasticity of the chlorinated rubber film constituting the preferred solid base encapsulating stratum is sutficient to permit the controlled flow of hard metal such as stainless steel at room temperature under metal forming forces beyond the elastic limit of the metal, e.g., of the order of about 100,000 pounds per square inch without any measurable decrease in film thickness as a result of shear and any noticeable compressive deformation of the film and without any breaking of the film.

Once the film is broken away from the metal surface, the steel wearing surface of the die exposes the underlying base metal and causes harmful seizing, scoring and galling of the workpiece due exclusively to the failure of the solid film.

The critical nature of the satisfactory lubricant material for interposition between the resin capsule and the steel die is further emphasized by other experiments made by the inventors herein to compare the satisfactory oleamide lubricant in Example I, the satisfactory low molecular weight polyethylene emulsion lubricant of Example II below and the chlorowax 40 lubricant of Example III below with the following lubricant coatings found to be unsatisfactory in the same manner as lard oil, lube A, by the test of Erample I.

Instead of an organic solvent solution of oleic acid amide, e.g., 10% solids in 1,1,l-trichloroethane, there may be applied oleic acid amide emulsified in water as the top coating. This water emulsion is preferred for application to the organic solvent solution since the latter tends to leave residual solvent which must be driven off by thorough drying and/or baking. Residual solvent is not left behind upon evaporation of the emulsion. A typical emulsion formula which is suitable is as follows:

Oleamide water emulsion lube B Oleamide 10.00 Nacconal NRSF (sodium salt of an alkylated napththaleue sulfonate) 3.00 Water 87.00 Concentrated aqua ammonia 0.04 Sodium nitrite 0.05

To emphasize the unique lubricating action which is achieved in a very limited and selective class of lubricant modifiers, the following table illustrates lubricants which are not operative and which cause seizing, galling and scoring of the workpiece as a result of lubricant failure and tearing away of the underlying encapsulating film and cold-forming forces.

Unsatisfactory lubricants on chlorinated rubber capsule for 90 Ls of stainless steel cold-forming by method of US. Patent No. 2,971,556

White lead in linseed oil Graphite Molybdenum disulfide Glyceryl ester of rosin Tricresyl phosphate Sperm oil Lard oil Spermaceti Polyvinyl stearate Vinyl stearate Polystearyl methacrylate Dibutyl tin disulfide Lauryl alcohol Lauric acid Oleic acid Soya trimethylene diamine diacetate Tallow trimethylene diamine dioleate Actadecine Actadecane Soya trimethylene diamine Tallow amine acetate N-coco amino butyric acid Dicocomethyl amine Hydrogenated tallow amine acetate EXAMPLE II This example illustrates application of low molecular weight polyethylene emulsion as lubricant coating to encapsulated tube blank using chlorinated rubber as in Example I. The base coating was made on a stainless steel blank as in Example I and a top coating of polyethylene emulsion was applied after the base coating was dried.

Following are examples of polyethylene emulsions which are obtainable from commercial sources and which are used successfully in accordance with the present invention.

Commercial polyethylene and polypropylene lubricant modifiers Emulsion: Solids as used, in water Mixed polyethylene propylene glycols of melting points 37-110 C Low molecular Weight polyethylene, mo-

lecular range 400-16,000, softening range 90105 C Atactic linear polypropylene of molecular weight range 400-1600 -20% There also may be used the homologous polymer atactic linear polypropylene of molecular weight range 400- 16,000 of the above table having a softening point range of above 37 C. and up to 110 C. Various fractions of the polyethylene and polypropylene materials of the above characteristics are available commercially as by-products of low molecular weight recovered from commercial polymerizations. All of these materials are obtainable in aqueous emulsion containing conventional emulsifying agents, e.g., organic sulfonates or non-ionic detergents and in varying concentrations up to about 35 of polymer suspended in water.

The metal blank coated as outlined above was formed into an L and the coating was tested by non-destructive apparatus called the Dermitron non-destructive thickness 10 tester made by the Unit Process Assemblies, Inc. The test disclosed that the straight blanks before forming had an encapsulating film coating thickness averaging 1 mil. These same blank pieces subsequently formed into Ls tested out as having a residual encapsulating film thickness of 1 mil.

EXAMPLE III This example illustrates the use of solid encapsulating film of waxy polyethylene glycol solution as lubricant over chlorinated rubber capsule in the method of Example I. In this example an aqueous emulsion of a waxy ethylene glycol polymer of molecular weight 4000-6000 was used. This composition had a softening point within the preferred range, e.g., above 37 C. and below C. Additional examples of polyalkylene glycols, of about the same molecular weight range, e.g., above 2500 and up to 6000, are phenolic terminated polyalkylene glycols of melting points 37110 C., such as:

Tergitol XD Tergitol NP-40 Tergitol NP-3S The forming operation as set forth in Examples I and II was carried out.

A satisfactory bend was made equal to lube B.

EXAMPLE IV This example illustrates the use of a copolymer of vinyl chloride, vinyl acetate and carboxylic acid, VMCH and shows that a satisfactory bend was made using oleamide as the top layer by the method of Example I.

In the foregoing examples there have been illustrated suitable lubricant modifiers such as oleamide, mixed polyethylene polypropylene glycols of melting points 37- 110 C., phenolic terminated polyalkylene glycols of melting points 37-110 C. like Tergitol XD, Tergitol NP-40, Tergitol N P-35; low molecular weight polyethylene and polyethylene glycols of melting points 37110 C.

The following lubricant modifiers are also suitable as the principal ingredient of the top coating deposited from either volatile organic solvent or water emulsion:

Chlorinated paraifin of melting point 37-110 C.

Eicosane Myristyl myristate Tallow trimethylene diamine Stearonitrile Polyethylene glycol 600 dilaurate Dimethyl dihydrogenated tallow ammonium chloride Dimethyl hydrogenated tallow furfuryl ammonium chloride Methyl trihydrogenated tallow ammonium chloride Ethoxylated hydrogenated stearamide of melting point 50-50, 30-70 or 7030 mixture of cetyl alcohol and stearyl alcohol Upon comparing the successful lubricant modifiers set forth in the examples hereinabove and the unsuccessful lubricant modifiers which are also set out above, a surprising contrast of the successful cold-forming operation will be seen employing the preferred and limited class of lubricant modifiers. It will be appreciated that the coldforming method and apparatus disclosed and claimed in co-pending application Serial No. 286,880, filed May 28, 1963, and in US. Patent No. 2,971,556, granted February 14, 1961, serves as a testing system to determine the operativeness or inoperativeness of the lubricant modifier. In the instance that the lubricant is in the satisfactory category as diclosed herein a very low coetficient of friction of the order of 0.01 to 0.02 in relation to the underlying enscapulating film against a polished steel die forming surface is achieved. This result is demonstrated by the fact that, as set forth in detail in Example I, coldforming of the hard metal occurs without any change in 1 1 thickness of the encapsulating coating or of the lubricant modifier and only the underlying metal suspended in the solid, hard substantially non-destructible encapsulating medium is caused to flow by the cold-forming forces which are in excess of the tensile and shear limits of the metal being formed.

It will, therefore, be appreciated that in this aspect of cold-forming utilizing the new and unexpectedly useful lubricants of the invention that the cold-forming apparatus employs a novel non-destructible encapsulating medium as a means to suspend the metal workpiece in a nonscoring relation to the metal of the cold-forming die and the lubricant modifier in tightly adhering relationship to the encapsulating medium effectively provides a new and positive apparatus means for successfully achieving coldforming under stresses beyond the elastic limit of the workpiece. The advantages in such apparatus apart from the precision of forming which the apparatus is capable of achieving lies also in the fact that heating of the metal is avoided, thereby prevenitng structural changes which are the rule rather than the exception in many of the hard alloy systems, for example in aluminum systems, iron systems, chromium systems, etc.

Having thus disclosed the invention, what is claimed is:

1. A volatile solvent dispersion of a solid film-forming lubricant adapted to adhere as an encapsulating lubricating film to a clean metal base, said solution consisting of a mixture of (1) a hard, tough polymer selected from the group consisting of chlorinated rubber, a tripolymer of 87- 95% vinyl chloride, 12-5% vinyl acetate and 0.5-2.5 of unsaturated carboxylic acid and copolymer of 60-85% vinyl chloride with 40-15% vinylidene chloride; ('2) an organic lubricant material having a melting point in the range of 37-1 C. and a coefiicient of friction between said polymer and steel of 0.01-0.02, said lubricant material selected from the group consisting of oleic acid amide,

mixed polyethylene-propylene glycol, polyethylene of molecular weight 400-16,000, and atactic linear polypropylene of molecular weight 40016,000, the ratio of said lubricant material to said polymer varying from about 3:1 to about 1:3; and (3) the remainder being volatile solvent containing a minor proportion of a chlorinated hydrocarbon and a major proportion of a non-polar liquid selected from the group consisting of aromatic hydrocarbons and aliphatic hydrocarbons whereby upon coating a 25% solids solution of said dispersion upon a metal base there is deposited the lubricant material as a surface film.

2. A solvent solution as claimed in claim 1 wherein said chlorinated hydrocarbon is 1,1,l-trichloroethylene, said non-polar hydrocarbon solvent is xylol; said polymer is chlorinated rubber and said lubricant compound is oleic acid amide.

3. A solvent solution as claimed in claim 1 wherein the proportion of oleic acid amide to polymer is from 1:2 to about 1:9.

4. A solvent solution as claimed in claim 3 wherein said oleic acid amide is emulsified in water before being dispersed in said solvent.

5. A metal part encapsulated with a hard tough polymer selected from the group consisting of chlorinated rubber, a tripolymer of 87-95% vinyl chloride, 125% vinyl acetate and 05-25% of unsaturated carboxylic acid and copolymer of -85% vinyl chloride with 40- 15% vinylidene chloride and having a lubricant coating over said polymer, said lubricant having a melting point in the range of 37110 C. and a coefficient of friction between said polymer and steel of 0.01-0.02, said lubricant selected from the group consisting of oleic acid amide mixed with polyethylene-propylene glycol, polyethylene of molecular weight 400-16,000, and atactic linear polypropylene of molecular weight 400-16,000, the ratio of said lubricant to said polymer varying from about 3:1 to about 1:3.

References Cited by the Examiner UNITED STATES PATENTS 203,346 5/1878 Kennerson 252-49.3 X 2,053,045 9/1936 Ralston et a1. 252-50 2,119,149 5/1938 Bishop 252-652 2,223,037 11/1940 Ihrig 252-9 2,293,420 8/1942 Wick 72-46 2,331,547 8/1943 Gessler et al. 117-75 2,353,198 7/1944 Soday 72-46 2,599,803 6/1952 Ballard et al. 252-56 2,686,488 8/1954 Montgomery 72-46 2,990,943 7/1961 Turinsky 252-34 X 3,021,941 2/1962 Huet 252-51.5 X 3,030,229 4/ 1962 Esswein et al. 117-75 3,110,413 ll/1963 McKay et al. 72-146 3,124,531 3/1964 Whitzel et al. 252-52 FOREIGN PATENTS 445,148 4/1936 Great Britain.

OTHER REFERENCES Kalichevsky et al.: Petroleum Refining With Chemicals (1956), Elsivier Publishing Company, New York, page 572 most pertinent.

DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

1. A VOLATILE SOLVENT DISPERSION OF A SOLID FILM-FORMING LUBRICANT ADAPTED TO ADHERE AS AN ENCAPSULATING LUBRICATING FILM TO A CLEAN METAL BASE, SAID SOLUTION CONSISTING OF A MIXTURE OF (1) A HARD, TOUGH POLYMER SELECTED FROM THE GROUP CONSISTING OF CHLORINATED RUBBER, A TRIPOLYMER OF 8795% VINYL CHLORIDE, 12-5% VINYLL ACETATE AND 0.5-2.5% OF UNSATURATED CARBOXYLIC ACID AND COPOLYMER OF 60-85% VINLY CHLORIDE WITH 40-15% VINYLIDENE CHLORIDE; (2) AND ORGANIC LUBRICANT MATERIAL HAVING A MELTING POINT IN THE RANGE OF 37-110*C. AND A COEFFICIENT OF FRICTION BETWEEN SAID POLYMER AND STEEL OF 0.01-0.02, SAID LUBRICANT MATERIAL SELECTED FROM THE GROUP CONSISTING OF OLIEC ACID AMIDE, MIXED POLYETHYLENE-PROPYLENE GLYCOL, POLYETHYLENE OF MOLECULAR WEIGHT 400-16,000, AND ATACTIC LINEAR POLYPROPYLENE OF MOLECULAR WEIGHT 400-16,000, THE RATIO OF SAID LUBRICANT MATERIAL TO SAID POLYMER VARYING FROM ABOUT 3:1 TO ABOUT 1:3; AND (3) THE REMAINDER BEING VOLATILE SOLVENT CONTAINING A MINOR PROPORTION OF A CHLORINATED HYDROCARBON AND A MAJOR PROPORTION OF A NON-POLAR LIQUID SELECTED FROM THE GROUP CONSISTING OF AROMATIC HYDROCARBONS AND ALIPHATIC HYDROCARBONS WHEREBY UPON COATING A 25% SOLIDS SOLUTION OF SAID DISPERSION UPON A METAL BASE THERE IS DEPOSITED THE LUBRICANT MATERIAL AS A SURFACE FILM. 